feat: scanned script

configs/packages/default.nix

@@ -114,6 +114,7 @@ in {
     bc # calculator
     pari # gp -- better calculator
     scripts.infschmv
+    scripts.scanned
     scripts.default-gateway
     scripts.showkeys-toggle
     scripts.favicon

packages/scripts/default.nix

@@ -343,6 +343,13 @@ in rec {
     esac
   '';
 
+  # ref https://tex.stackexchange.com/a/502542
+  scanned = pkgs.writers.writeDashBin "scanned" ''
+    [ $# -eq 1 -a -f "$1" -a -r "$1" ] || exit 1
+
+    ${pkgs.imagemagick}/bin/convert -density 150 "$1" -colorspace gray -linear-stretch 3.5%x10% -blur 0x0.5 -attenuate 0.25 +noise Gaussian "scanned-$1"
+  '';
+
   nix-index-update = pkgs.writers.writeDashBin "nix-index-update" ''
     mkdir -p $HOME/.cache/nix-index
     tag=$(git -c 'versionsort.suffix=-' \